<!DOCTYPE html>
<html>
 <head>
  <style>
    div {
      height: 100px;
    }
    #basic {
      /* "none" should split into two and take each neighboring value. */
      background: linear-gradient(to right in srgb, color(srgb 0.5 0 0), color(srgb 0.5 0.5 0.5) 50%, color(srgb 1 0.5 0.5) 50%, color(srgb 1 1 1));
    }
    #multipleNone {
      /* "none" and "none" gives zero. */
      background: linear-gradient(to right in srgb, color(srgb 0 0 0), color(srgb 0.0 0.5 0.5) 50%, color(srgb 1 0.5 0.5) 50%, color(srgb 1 1 1));
    }
    #allNone {
      /* "none" and "none" gives zero. */
      background: linear-gradient(to right in srgb, color(srgb 0 0 0), color(srgb 0 1 1));
    }
    #noneHue {
      background: linear-gradient(to right in oklch, oklch(0.2 0.1 90), oklch(0.8 0.4 90) 50%, oklch(0.8 0.4 180) 50%, oklch(0.3 0.2 180));
    }
    #noneHueLonger {
      background: linear-gradient(to right in oklch longer hue, oklch(0.2 0.1 90), oklch(0.5 0.3 90) 50%, oklch(0.5 0.3 180) 50%, oklch(0.8 0.4 180));
    }
    #transparentHueIsPowerless {
      /* oklch(0.627966 0.257704 29.2346) = "red"
         oklch(0.451981 0.31321 264.051) = "blue" */
      background: linear-gradient(to right in oklch, oklch(0.627966 0.257704 29.2346), oklch(0 0 29.2346 / 0) 50%, oklch(0 0 264.051 / 0) 50%, oklch(0.451981 0.31321 264.051));
    }
 </style>
 </head>
 <body>
  <div id="basic"></div>
  <div id="multipleNone"></div>
  <div id="allNone"></div>
  <div id="noneHue"></div>
  <div id="noneHueLonger"></div>
  <div id="transparentHueIsPowerless"></div>
 </body>
</html>
